Holding devices of this type are frequently required in performing surgical interventions in order to hold medical instruments of various types, such as retractors, video cameras, or endoscopes, in an established position for a fairly long period. Owing to the jointed design of the holding devices, it is possible for the surgeon to position with exactitude the medical instrument that is held in the instrument intake and, by stopping the joint or joints, to fix the position of the holding device that has been selected.
A generic holding device is known in the art, for instance, from patent US 2003/116167 A1. In this known holding device the joints consist of two joint members, which enter into active connection with one another by means of catching elements that engage with one another, where each joint comprises an inflatable balloon, which when it is expanded presses the catching elements into engagement with one another. The disadvantage with this known construction is that the carrier arm members immediately rotate toward one another when there is any drop in pressure in the bladder, because the reciprocal engagement of the catching elements of the joint members is produced exclusively by the applied pressure of the bladder.
An additional holding device is known for instance from patent DE 195 26 915 B4. With this known holding device, the joint members are locked in place with respect to one another by friction through the spring force of at least one spring element. This blocking is released pneumatically by vanes that are positioned in the joint and when acted upon by compressed air, for instance, ensure a release of the friction locking. Although holding devices of this type have been thoroughly proven in the art, the contact surfaces that are held together by the friction locking in fact cause problems with cleansing, because owing to the high contact forces required to produce a reliable friction lock, scratches can be produced on contact surfaces that in turn can form germ cells leading to soiling.
In addition, a holding device is known from patent DE 43 16 590 A1. With this known holding device, the joint mechanism takes the form of a toothed wheel work, where the engagement of the toothed gears configured as inner and outer wheel sprockets is directed parallel to the longitudinal direction of the carrier arm, that is, parallel to the axis of rotation, and the wheel sprockets are held engaged with one another by means of a pressure force acting axially. A disadvantage of this construction is that it requires extreme precision in manufacturing the wheel sprockets in order to ensure interlocking engagement of the teeth of both wheeled sprockets without free play. The axial spring force prevents only the separation of the two wheel sprockets, as it is not possible with this configuration to prevent free play in the horizontal direction.
It is consequently the object of the invention to create a holding device for medical purposes that combines ease of operation and reliable positionability with effective cleansing.